Fixed vertical spacing on alt selector for page.html

templates/nav.html

   {% if this._path != '/' %}
   <div class="text-center mb-3">
-    <div class="btn-group btn-group-toggle mb-2 px-2 text-monospace">
+    <div class="btn-group btn-group-toggle my-2 px-2 text-monospace">
       {%  for alt in get_alts() %}
         <a href="{{ '.'|url(alt=alt) }}" class="btn btn-secondary btn-md-light{% if this.alt == alt %} active{% endif %}">[{{ alt }}]</a>
       {% endfor %}